The in-situ solid-state NMR spectroscopy investigation of alcoholic lactose suspensions |
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Authors: | JL Crisp SE Dann M Edgar CG Blatchford |
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Institution: | 1. Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK;2. 3M Health Care Ltd., Drug Delivery Systems Division, Loughborough, Leicestershire LE11 1EP, UK |
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Abstract: | The polymorphic forms of lactose in alcoholic suspensions have been determined by 13C CP-MAS NMR spectroscopy, employing hand-made glass inserts. Suspensions of alpha lactose monohydrate (Lα·H2O) with particle size between 2 and 200 μm were prepared by 24 h reflux or by storage for 28 d in anhydrous ethanol without agitation. These suspensions were compared to an ethanolic sub-micron lactose suspension provided by a 3 M Health Care (Loughborough). The 13C CP-MAS NMR spectra indicated that Lα·H2O dehydrated to stable anhydrous alpha lactose polymorph (LαS) whilst suspended in ethanol. In addition, strong ethanol 13C resonances were observed for some samples, indicating a liquid–solid interaction between the ethanol and lactose surface. Replacement of ethanol with anhydrous methanol, n-butanol and 3-methylbutan-2-ol implied that the solvent mediated dehydration of Lα·H2O to LαS occurs as a result of sterically controlled interactions. |
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